X-linked adrenoleukodystrophy (X-ALD), a progressive genetic disorder, is caused by mutations in the ABCD1 gene, which encodes a peroxisomal ATP-binding cassette transporter (ABCD1) responsible for transport of CoA-activated very long-chain fatty acids (VLCFA) into the peroxisome for degradation leading to the accumulation of high levels of saturated, very long chain fatty acids (VLCFA) in plasma and tissues of the brain and adrenal cortex. Symptoms can begin in childhood or adulthood. Adult ALD patients typically develop adrenomyeloneuropathy (AMN), a debilitating neurological disorder, in their twenties (Engelen et al., Orphanet J Rare Dis. 2012; 7: 51). The Abcd1−/− mouse develops a phenotype similar to AMN, manifesting spinal cord axon degeneration as well as peripheral neuropathy due to affected dorsal root ganglion neurons (DRGs) (Pujol et al., Hum Mol Genet. 2002; 11:499-505). Transduction of central nervous system cells in vitro and in vivo using recombinant adeno-associated virus serotype 9 (rAAV9) vector for delivery of the human ABCD1 gene was previously reported. Unfortunately, intravenous delivery in young mice is associated with cardiac toxicity due to transgene overexpression. Delivery systems that provide non-toxic levels of ABCD1 in patients suffering from X-ALD or AMN would be highly desirable.